In order to serve the increased demand, wireless communication networks are becoming more diverse and complex, and subsequently are becoming more difficult to manage. A Self-Organizing Network (SON) simplifies and automates multiple processes to efficiently manage diverse communication networks.
Many SON algorithms require information about the coverage areas of cells in order to make better optimization decisions. However, it can be difficult to obtain cell coverage information for a network. Cell coverage information could be retrieved from the output of a network planning tool, but this information is not always available to a SON tool. In addition, network planning tools tend to use large amounts of data to determine cell coverage, so planning tools tend to be relatively slow and inefficient.
Typical algorithms attempt to estimate the coverage area of a source cell by identifying the closest cells in the network to the source cell and using information on the azimuth of the source cells to estimate a coverage distance for that cell. While these methods can produce acceptable results in networks where cells are laid out in a regular fashion, they tend to perform poorly in areas with an irregular placement of cells.
In addition, some algorithms have absolute distance thresholds in place to prevent against poor algorithmic decisions. For example, an Automated Neighbor Relations (ANR) algorithm may impose a maximum distance threshold beyond which cells are not added to neighbor lists. One problem with imposing such a threshold is that a single threshold is generally not suitable in all cases, especially when cell density varies.
For example, in rural environments, a large distance threshold such as 15 km may be suitable. However, if this threshold is used in an urban environment, distant cells may be added to the neighbor list of a source cell, resulting in poor system performance. In an urban environment, a distance threshold of 2 km to 4 km may be more suitable. However, if the distance threshold is set too low, neighbor cells may not be added, even though manual inspection shows that they should be.
Distance thresholds are generally applied to a large number of cells in a region such as all cells on a particular Radio Network Controller (RNC). While different distance thresholds may be applied on a per-cell basis, this is time consuming and error prone if done manually.
In practice, optimization engineers don't consider distances—instead, they look at cell tiers. Most RF engineers look at map and intuitively know how many tiers separate cells. However, it can be hard for an optimization engineer to provide a precise definition for a cell tier, or how to establish such a tier.
Most engineers will look at a map and make intuitive estimates about which cells are first tier neighbors of a source cell. Generally, these will be the closest cells to the source cells, with antenna pointing directions that are pointing towards the coverage area of the source cell. However, these intuitive decisions are difficult to translate into algorithms. Therefore, it is desirable to have an accurate and efficient tool that automates the tier counting process.